In the development of automatic transmissions, it is expected that claw shifting elements will be increasingly used, primarily because, compared to conventional frictional shifting elements, they are clearly more favorable in terms of the drag torques, such that the overall efficiency of the transmission can be increased.
It is known from the state of the art to keep closed both the friction-locking shifting elements, such as multi-disk shifting elements, and the positive-locking shifting elements or the claw shifting elements of an automatic transmission through hydraulically actuated pistons with a corresponding pressure.
Thereby, the pressure oil guidance for the pistons of the shifting elements takes place through rotating elements, which are sealed by means of gap-type seals, such as a slide bearing and/or rectangular rings. Upon the actuation of the shifting element, in particular with high coupling pressures, such rotary joints known from the state of the art exhibit, in a disadvantageous manner, losses as a result of leaks.
By contrast, in manual and automated transmissions and in dual-clutch transmissions, the largely synchronized claw couplings are actuated through shift forks. Thereby, the synchronization gear teeth are provided with an undercut, in order to prevent an accidental disengagement when there is a load. In a load-free state, the respective sliding sleeve is axially locked by spring-loaded balls. In addition, the shift forks are fixed in their axial position through suitable devices.
However, the spring-loaded balls require a great amount of installation space, which is not always present in automatic transmissions.
U.S. Pat. No. 5,667,330 shows a claw coupling with a centric, single-sided piston that is able to be subject to pressure and a return spring. With the known claw coupling, a finger is provided for actuation; this takes hold through a slot hole in a shaft. With the known claw coupling, the actuation of the claw coupling is carried out inside the shaft.
From DE 10 2009 026 707 A1, an arrangement with at least one claw coupling for the shiftable coupling and decoupling of a shaft of an automatic transmission with a planetary design with at least one component is known, whereas the shaft is connectable to a component of a planetary gear set and whereas the claw coupling is arranged in a manner that is essentially centric inside a sun gear of the planetary gear set. Thereby, an arrangement that is neutral in respect of installation space is to be created.
Furthermore, DE 10 2009 026 710 A1 shows an arrangement with at least one claw coupling, which is connectable to at least one component of the transmission, whereas the claw coupling is arranged essentially inside a bearing carrier of the transmission, and features a stationary cylinder.